Japanese Laid-Open Patent Publication No. 2000-67824 discloses the use of air batteries as a so-called battery pack. More specifically, the battery pack of Japanese Laid-Open Patent Publication No. 2000-67824 has three button-type air batteries vertically connected in series and placed in a metal exterior can, with an insulating sheet interposed between the air batteries and the exterior can, such that the air batteries are insulated from the exterior can by the insulating sheet.
Each of the air batteries includes: a cathode can formed of a metal material in a bottomed-cylindrical shape with one end open and storing therein an anode active material e.g. zinc and an electrolyte e.g. aqueous potassium hydroxide solution; and an anode cap closing the open end of the cathode can.
In the battery pack of Japanese Laid-Open Patent Publication No. 2000-67824, however, the weight ratio of the anode plate (anode cap) is large. This causes unsolved problems such as difficulty in weight reduction and hindrance to size reduction.